Geologists have ruled out north-east Scotland as the source of Stonehenge’s six-tonne Altar Stone, overturning a prominent 2024 theory. A new study published in the Journal of the Geological Society indicates the sandstone slab likely originated from a different location, though its exact home remains unidentified.
Geological testing narrows the search for the Altar Stone
An international team of scientists conducted what Professor Duncan Pirrie, Emeritus Professor at the University of South Wales and leader of the study, called the most comprehensive geological investigation of the Altar Stone ever undertaken
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A new study exploring the origins of the six tonne Altar Stone at Stonehenge has ruled out a theory that it came from an area of Scotland. https://t.co/d084OqXvps
The investigation focused on the Orcadian Basin in north-east Scotland, which a 2024 study had suggested as the likely origin. That earlier research, which involved specialists from universities in London, Wales, and Australia, hypothesized the stone came from the Old Red Sandstone of the Orcadian Basin, a journey of more than 400 miles from Stonehenge. However, the latest findings, reported by BBC, show that none of the locations examined in that region possess the same set of characteristics as the Altar Stone.
Ruling out potential source areas is just as important as identifying new ones,
Pearce said, adding that every location eliminated narrows the search and brings us closer to discovering where the Altar Stone originated.
Fieldwork in Scotland and laboratory analysis
To test the Scottish theory, researchers collected approximately 70 samples from exposed rock formations across the region. The fieldwork involved navigating difficult weather conditions, including storms, to gather material for testing. One of my colleagues was there recently and he got caught in the storms, which isn’t ideal field weather for geology. We collected about 70 samples, brought them back to the laboratories, and examined them,
Pearce told The Guardian.
The Altar Stone is a 4.9-metre sandstone slab that is unique among the stones at Stonehenge. Previous researchers, including Chris Kirkland from Curtin University in Australia, had examined mineral grains in modern stream sediments around Stonehenge and found no trace of the distant material that glacial delivery would have left behind. A separate study in the Journal of Quaternary Science modeled ice flow from Scotland and concluded that ice could at most have carried the stone toward Dogger Bank, which is now beneath the North Sea, rather than to Salisbury Plain. Kirkland noted that a possible glacial path is not evidence that the stone actually followed it.
Altar Stone mystery continues as theory overturned https://t.co/Mm3gNxV3oh
Shifting theories on the stone’s journey
The scientific understanding of the stone’s movement has changed significantly over the last several years:
- For almost a century, the prevailing view was that the Altar Stone came from west Wales, similar to the smaller bluestones which traveled around 225km.
- In 2020, geologists showed this was incorrect.
- In 2024, researchers hypothesized the stone came from north-east Scotland, roughly 400 miles (640 km) or more from Stonehenge.
- In 2026, new analysis by Professor Duncan Pirrie and colleagues undercuts the theory that the 6-ton slab came from northeastern Scotland.
The geologists stop short of ruling out Scotland entirely, but the current research indicates the Orcadian Basin is unlikely to be the source.
Implications for Neolithic history
Tracing the origin of the six-tonne slab is considered vital for understanding the technological capabilities and mobility of Neolithic communities. Stonehenge itself was constructed in several phases between approximately 3000 and 1600 BC. Finding the source would provide valuable new insights into the stone’s journey to Salisbury Plain.
Mike Pitts, a prominent Stonehenge expert who was not involved in the study, said that identifying the origin would be an exciting prospect. He noted that doing so would help place the Altar Stone within the context of the people who moved it, allowing researchers to see the terrain through their eyes and know exactly where the journey began.
Stonehenge Altar Stone mystery continues as Scotland theory overturned. https://t.co/fAexytqYjv